Week 2 Notes- General Ecology
Week 2 Notes- General Ecology BIOL3863 001
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This 7 page Class Notes was uploaded by Ashley on Monday September 14, 2015. The Class Notes belongs to BIOL3863 001 at University of Arkansas taught by John Willson, in Summer 2015. Since its upload, it has received 58 views. For similar materials see General Ecology in Biosystem Engineering at University of Arkansas.
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Date Created: 09/14/15
b Week 2 General Ecology Notes Statistics 0 An objective mathematical way of attaching a level of confidence to conclusions that can be drawn 0 Use measures of central tendency and variation 0 pvalue value between 0 and 1 that describes the probability that we are making a false conclusion falsely rejecting the null hypothesis 0 Alpha a value predetermined level of confidence you are willing to accept usually 005 5 o If pvalue is lower than alpha value we reject the null hypothesis and say that a difference is statistically significant Ttests and ANOVA a b T P P E L a l D o a l o D 6 I E o E 3 C C m D 2 Site A Site B Site A Site B There is a probability of 040 40 of obtaining these data if the null hypothesis is true there is no difference between sites There is a probability of 001 1 of obtaining these data if the null hypothesis is true there is no difference between sites Correlation or Regression 0 When comparing relationships among two variables we usually use a dotline graph and use regression analysis to assess relationships Simple Experimental Design EX Effects of food supplementation on rattlesnake populations Control 46334 Acorn Supplemented 104676 Results of snakes Standard Error Bars Usually if standard errors do not overlap it is a good indication that the treatments P 0049 are significantly different There is a 49 chance that there is 39 actually no difference between trts We are 951 confident that there is ONmeO U G x 395 C U39 4 II a real difference among trts C g 60 96 Trts are significantly different at a 00 Q 005 level Q Q o Probabilities and Confidence 0 Nothing is proven if you reject the null o If you do not reject the null 1 Really is no effect 2 Effect is weak and more data are needed 0 Examples of Experimental Design end of Ch 1 I Brown Trout Introductions I Vegetation Succession I Hubbard Brook nutrient cycling amp deforestation I Vulture Declines ECOLOGY S EVOLUTIONARY BACKDROP CAHPTER 2 0 Evolution is driven by interactions among organisms and between organisms and their environment 0 Ecologies of organisms are shaped by their evolutionary history ultimate explanations o How does it happen Darwin and Wallace s observations Observation all organisms have high fecundity Observation resources limited most offspring die Malthus Inference results in a quotstruggle for existence Observation individuals are different and differences are heritable Inference survival is nonrandom individuals with favorable traits have more offspring o Inference frequencies of traits in populations will change over time with favorable traits accumulating o DARWIN S CONCLUSION I Evolution by natural selection Change in the relative frequency of a trait gene or allele within a population over time o Heritable Variation 0 Traits Phenotype the observable characteristics of individuals 0 Influenced by genetics heritable and environment plasticity not heritable OOOOO O 0 Genetic variation arises through random mutation Selection acts on traits but only heritable traits evolve 0 Differential Survival or Reproduction O 0 Fitness Ability to survive and reproduce contribute to the future gene pool of the population quotThe theory of evolution says that species originate and evolution proceeds by random chance quotThe chances that life just occurred are about as unlikely as a typhoon blowing through a junkyard and constructing a Boeing 747quot IS EVOLUTION RANDOM NO Variation mutation can be random but selection is incremental and profoundly nonrandom o Studying Evolutionary Ecology 0 Geographic variation within a species Local Adaptation 1 Local adaptation to an environment requires a Sufficient heritable variation on which selection can act b Environmental selecting force strong enough to counteract population genetic mixing hybridization 2 Evidence for local adaptation requires evidence that the phenotypic trait is under some genetic control not simply a plastic response to the immediate environment 0 Sapphire Rockcress common garden experiment Water use efficiency mole of CO2 gained per mol of H20 lost x 10 3 0 0 Problem Rare perennial herb 19 populations threatened by urban expansion I high elevation short I low elevation tall threatened by urban sprawl Objective To determine the feasibility of reintroduction of this species into other environments the possibility of local adaptation on population traits needs to be examineol Reject the null evidence for local adaptation P 0009 20 P 00001 40 P 0001 15 A 30 A E E E E 1 H 9 is E g 10 g 20 g E a z g g m o 5 1O 0 Low High Low High Low High elevation elevation elevation elevation elevation elevation Mechanistic evolutionary experiment Poecilla reticulate Significant correlation between guppy color patterns and intensity of predator risk Endler 19789 Do predators cause the evolution of coloration a R 13 12 Weak predator E 11 I No predator 8 quot o 8 10 Strong predator U 9 8 I l l o is 10 20 Time months 0 Ecology of Speciation What is a species 0 Mayr amp Dobzhansky 1930 s Populations of different biological species biospecies do not interbreed in nature and produce viable offspring o Orthodox scenario for speciation I Geographic isolation I Natural selection in local environments I Reproductive isolation between species during secondary contact hybrids have low fitness a For example different mating seasons calls coloration b Or simply that they produce infertile offspring o Allopatric Speciation occurs after geographic isolation o Sympatric Speciation occurs in same geographic location 0 Thought to be relatively rare 0 Often through microhabitat selection eg feeding on different plants 0 Convergent evolution results in structures that are analogous but not necessarily homo0g o Analogous Similar in form or function 0 Homologous Derived from equivalent structures 0 Parallel evolution 0 Started ancient common ancestors 0 Similar evolutionary pathways resulting similar forms in two locations 0 EX legless lizards o Constraints on Evolution by Natural Selection 0 Natural selection does not result in a perfect match between organisms and their environments I Evolutionary history Changing Environment Ecological tradeoffs Sexual selection amp coevolution 0 Natural selection can bring about great changesBut it does so by modifying traits that are already present not by creating advantageous traits de novo o Lifehistory Evolution in gartersnakes Thamnophis elegans Reciprocal Transplant Experiment 0 Hypothesis 1 Differences in life history among populations are heritable have a genetic basis 0 Hypothesis 2 Populations are locally adapted to environments of their respective habitats 1 Neither hypothesis is supported Snakes at the lake are always larger no effect of source population 2 Both hypotheses are supportedStrong genetic effect snakes from the lake source always larger but individuals do best when raised in their source environment 3 H1 is supported but H2 is notSnakes from the lake source population are always larger no effect of raising environment 0 Changing environment In many cases we can think of organisms as adapted to past environments 0 Trade off a balance achieved between two desirable but incompatible features 0 Larger body size in the black swamp snake results in larger litter sizes but lower survival 0 Sexual selection Selection for traits that improve reproductive success but not necessarily survival 0 Often explains sexual dimorphism different phenotypes among sexes o Coevolution Reciprocal evolution between two species Can cause runaway evolution of traits evolutionary arms races ORGANISMS IN THEIR ENVIRONMENT CHAPTER 3 o Scales of biological organization Biosphere Landscapes Ecosystems Ecoogy Communities Populations Complexity Individual organisms Organ systems physioogy Organs Tissues Cells Cell Biology Subcellular organelle Molecules Biochemistry 0 Factors influencing geographic distribution 1 Access can the species get there 2 Favorable environmental conditions 3 Sufficient resources food etc 4 Interactions with other species 0 Conditions versus Resources 0 Conditions Abiotic or physicochemical characteristics of an environment I Not consumed or depleted by organisms I Temperature pH salinity 0 Resources Consumed or taken up by organisms in the course of growth reproduction and maintenance Carbon oxygen light Condition is lethal at some high intensity 0 Response Types to Conditions or concentration b Threshold response above which performano decreases rapidly Reproduction growth survival q adaptation harsh co 9 Vital rates are highest at o D some 0 timal level and low 0 Reproduction 390 m at extremes L O 8 Individual growth Optima differ between c g species or populations 5 Individual survival remember local 39139 lt1 0 conditions for one species might be optimal for another Intensity of condition gt 0 Temperature 0 Metabolism Enzymemediated processes by which energy and resources are I taken up from the environment I transformed within the organism I allocated to maintenance growth and reproduction I egested or released back into environment 0 Enzymatic reactions increase with temperature 0 Proteins denature above certain temperatures 0 Optima are different for different organisms o Acclimatization to Conditions 0 Many organisms can adjust to stress through behavior or physiology called acclimatization I It is usually a shortterm reversible process 0 Example Many plants and some animals acclimatize to cold by increasing levels of sugars in cells to resist freezing o Ectotherms Rely on external environment to regulate body temperature 0 Endotherms Rely primarily on metabolic heat generation
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